Abstract

OBJECTIVE • To determine whether muscarinic receptor antagonism affects stretchinginduced release of ATP. MATERIALS AND METHODS • Mucosal strips, dissected from guinea pig (male, 450g; n = 10) urinary bladders, were placed in horizontal organ baths and superfused with Ca2+-free Tyrode’s solution. • Superfusate samples were taken pre- and post- intervention (rapid stretching or relaxation) and ATP concentration was quantified using a luciferin–luciferase assay. • The effect of muscarinic acetylcholine receptors antagonism on ATP release was assessed by addition of methoctramine (1 μM) and 4-DAMP (10 nM). RESULTS • Rapid stretching (0 to 13.3 ± 1.2 mN; no. strips = 20) increased ATP in the superfusate to a median threefold increase over basal levels. • After a period of equilibration, tension in the mucosal strips relaxed until it had reached a new steady-state after 60 min and stretching was repeated. In the presence of 4-DAMP (10 nM) or methoctramine (1 μM), ATP concentrations after stretching reduced to 61% or 20%, respectively. By contrast, ATP concentrations in mucosa-matched controls, perfused with vehicle, increased in response to stretching by 391% and 1500%, respectively. • Rapid relaxation also stimulated ATP release. This release did not appear to be sensitive to 4-DAMP or methoctramine. CONCLUSION • An alteration of resting mucosal tension is the key determinant of ATP release, as 3 ATP is released from the mucosa in response to both stretching and relaxation. • Muscarinic receptor antagonism inhibits stretching-evoked ATP release from bladder mucosa, suggesting that anticholinergic agents used to treat human lower urinary tract pathologies act on urothelial